Method of and apparatus for lapping gears



July 10, 1934. H. JACKOWSKI METHOD OF AND APPARATUS FOR LAPPING GEARS Filed Feb. 5, 1931 3 Sheets-Sheet l fie adow i,

ylffor'izeys.

H. JAcKows'Kl METHOD OF AND APPARATUS FOR LAPPING GEARS July 10, 1934.

5 Sheets-Sheet 2 Filed Feb. 5, 1931 Fig. 4

July 10, 1934.

H. JACKOWSKI File d Feb 5. 1951 Fig. 44

METHOD OF AND APPARATUS FOR LAPPING GEARS 5 Sheets-Sheet 3 fix Fly. 20

- section EE of Fig.

i an. unhardened tooth.

Patented July 10, 1934 UNITED STATES PATENT OFFICE 1,966,172 METHOD OF AND APPARATUS FOR LAPPIN G GEARS Hermann Jackowski, Remscheid, Germany, as-

signor to firm: W.

Ferd. Klingelnberg Siihne,

Remscheid-Berghausen, Germa .mplication February 5, 1931, Serial No. 513,876 In Germany-February 11, 1930 16 Claims.

The invention relates to a method of and machines for, making gears, viz: spur and bevel gears which are insensitive to displacements of their axes from the theoretically correct relative positions, the gears running noiseles sly even in cases where the gears change their relative positions while in service.

Another object of the invention is to eliminate deformations or distortions of the tooth profiles which usually occur when grinding and lapping gears, by making them run with a fluid abrasive compound, and also by applying predetermined tooth corrections to the gears to be ground in, to give the gears a maximum possible degree of accuracy of flank profile.

In the accompanying drawings,

Fig. 1 represents a longitudinal section taken through the machine intended for lapping spur gears.

Fig. 2 is a cross section through the headstock of the driven gear, the section being taken on line AA of Fig. 1.

Fig. 3 is a view of the headstock for the driven gear.

Fig. 4 is a longitudinal section through the machine for lapping bevel gears.

Fig; 5 is a cross section on line through the headstock of the driving gear.

Fig. 6 shows two bevel gears in the correct relation.

Figs. 7-10 show. two bevel gears in various displaced relative positions.

Fig. 11 is a longitudinal section CC of Fig.

.12 through the base and the mechanism, by which the displacing movements are produced, as seen in the direction of the arrow D.

Fig. 11a is a vertical sectional view through bolt 19 along the dotted lines shown in Figs. 4 and 11.

Fig. 11b is an end view 01' the crank 43 of Fig. 11, showing its two positions, one of these positions being indicated by dotted lines. v

Fig. 12 is'a close-up plan view representing a n 11 of the mechanism producing the displacing movements.

Fig. 13 shows two spur gears in the correct engaged positions.

Figs. 14-16 show two spur gears in various displaced relative positions.

Fig. 17' is. a correct involute tooth profile of Fig. 13 is a tooth profile distorted by the hardening effect.

Fig. 19; is a. tooth profile which has been 3-13 of Fig. 4

\ when rolling is largest those zones having the largest deformed by running the gears together in a fixed, rigid position.

profile with grinding bottom portions. In each of the, Figs. 18, 19 and 20 thecorrect involute profile is shown in dotted lines.

The eflorts to obtain quiet-rurming spur, heliin practice, have been essening them together under pressure.

- With hardened gears, eiforts have been made This method; too, tailed to result in the desired success. It'became evident that the velocity with which the tooth flanks slide upon each other onthe top portion of the tooth and decreases. towards the pitch circleline where it drops to zero, that is, a pure rolling motion takes place at this line. From the pitch circle line, the sliding velocity again increases towards the root of the tooth. As a consequence of the different sliding velocities and difierent densities of grain, the grinding action of the abraflanks is also of a sliding movements while it is smallest at the zone of the pitch circle line.

When considering that, normally, by hardening the teeth, a shrinking action takes place so that the unhardened tooth (Fig. 17) after being hardened. approximately takes the outline of Fig. 18, it will be obvious that the tooth thickness has thickness has been increased just at that zone where the grinding action is smallest, that is in purpose on which nated, but, on the contrary, the departures from the correct involute profile have been intensified.

Even when in the theoretically correct relative positions, such gears are not able to run quietly. Trying to obtain an additional grinding action in the pitch circle zone by running the gears to be lapped in mesh with a properly profiled, hardened master gear, and shifting the gears both axially and radially while running together, failed to prove successful in obtaining a theoretically correct tooth profile, since, as will be seen from Fig. 18, the hardened gear becomes distorted in its outline by the action or the hardening process, and the master gear will be subjected to approximately the same grinding action of the lapping compound as the gear to be corrected.

If, for example, a spur gear b has been lapped with a master gear a, and the same master gear is used to lap a spur gear 0, the gears b and 0, due to the increasing and different wear of the master gear a when meshing with the various gears b and 0, etc. will show different tooth profiles which fail to give a proper, silent rolling movement. And, finally, for the same reason, the attempt to have a hardened gear run with several master gears with various pressure angles has had no practical success.

This invention is based on the experience that merely the high accuracy of a ground tooth flank does not afiord any reliability as toquiet running conditions. It is rather the accuracy of the assembled relative positions that determines the quietness in service. Since, in practice, because of purely economical reasons of manuiacture, the assembly and bearing accuracies do not exceed a given limit (in most of cases, hundredths, and in particular cases, thousandths of an inch), even ground gears having, usually, a larger degree of accuracy (up to ten-thousandths of an inch) cannot gain any particular importance.

The invention relates to a method by which it will be possible to make gears that are insensitive to all relative axial displacements from their theoretically correct positions which occur in practice, and that run quietly even when subiected to axial displacements in service and inaccuracies of assembly. This insensitiveness of the tooth flanks is obtained by imparting to the hardened gears those axial displacements to which they may be subjected later on under service conditions when assembled, suitable machines tobe described below being used for this a fine-grained, fluid lapping compound is fed to the gears while they are running together.

Since, of course, the quietness of rolling gears also depends on the correctness of the tooth profile, it will be necessary for each method of grinding such'gears to take care to obtain the correct profile or to re-establish the same, in the case, it should be changed by effect of hardening distortions. Therefore, in order to obtain such a correct tooth profile, the invention embodies another added feature, namely, to give or grinding allowance to the accordance with a surplus of stock gears to be made insensitive in the present method, at the zones of the largest wear of the flanks, before hardening the gears and when toothingv them i (Fig, 20)"; The said i ranged at right angles to each other.

surplus of material is ground 'ofi by employing machines embodying the principle of the inventive idea and by such an amount that the correct involute flank profile will be re-established. In

addition, the whole depth of tooth is made higher I 'and bottom portions, on the lapping machine,

and firstly in positioning the headstocks in the theoretically correct relations, as shown by Fig. 6 for bevel gears and by Fig. 13 for spur gears. The displacing movements (see Figs. I--10 and 14-16) as measured at the place of destination of the gears, then, are adjusted on the machine both as to their amplitudes'and in the ratio of their velocities. that the gears are caused to revolve about their axes, while a fluid grinding compound is forced betweentheir teeth and, furthermore, the dis-- placing mechanism brings the gear axes out of their theoretically correct positions, that is, displaces them one against the other in a similar manner to that of service conditions through the influences of the elasticity of bearings, assembly errors and the like. The combined addi- The machine is next started so i tional movements in conjunction with the rolling and sliding velocities of the rolling flanks result in a rapid curved movement 01 the abrasive grains.

In the following, two styles of machines will be described by way of example whichare used for making the gears insensitive and polishing them in accordance with the present invention.

The object of the lapping machine is to run the gears to be lapped in engagement under a given pressure, to force a fluid grinding compound between the teeth and to bring the gears while running into the different displaced relative positions as described above.

The displacing movements oi the gears may be obtained by the combination of various individual movements. These individual movements may comprise a reciprocating movement in the direction 01! the axis of one gear, a reciprocating movement at right angles to the latter, and either an up and down swinging motion about the centre bearing, or a waving or wabbling motion, the

periods and'the amounts of these three movements being different.

To meet the requirements indicated above, namely to imitate the displacements of the gear axes occurring gearsto be lapped and to impart them to the gears while being lapped, two types of machines are possible: either a combined machine suited for lapping both spur-and bevel gears or amachine for lapping spur gears and another one for lapping 'bevels. In the following description, .the second case will be dealt with both a machine for lapping spur gears and a machine for lapping bevel gears being described.

Generally, the lapping ma'hines consist of two headstocks which may be adjusted along two guide ways on a common base the ways being ar- On the machine which may be used for lapping the two kinds of gears, i.e. spur and bevel gears, one of the at the place of destination of the headstocksis rotatable on a circular plate by 360 degrees so that it will be possible to so set the axis of a spur gear that it will be parallel with that of its mating gear, and to set the axis of a bevel gear to the required angle under which the gears are to be run together.

The machines .shown by the illustrations are designed as single-purpose machines which may be used for lapping spur gears and bevel gears, respectively.

With the spur gear lapping machine, Figs. 1, 2, 3. 11, 12, the two he'adstocks 1 and 2 are movable along the guide ways 3 of the base 4. I

The headstock 1 carrying the driving gear 5, may be moved'in a straight line in the direction of the gear'axis, while the headstock 2 carrying the driven gear 6 may be moved in a straight adjusting the headstocks. Bymeans of the hand wheels '7 which are connected-to the screw spindles 11 through the shafts 8, helical gear 9 and spur gear 10 (Fig. 11) while said screw spindles, in turn, are connected to the headstocks through nuts 12, the headstocksmay be adjusted to the .I. proper centre distance of the gears to be lapped,

20 are tightened against the walls 21 and 22 of the.

- .base so that the headstocks are securely pressed against the bed ways. The screw' spindle 11 is supported at the hand-wheel end side in the base so as to be axially movable, while it the opposite end with the b'ock 24. The block may be adjusted in'the direction of the screw spindle axis and surrounds a cam 25 By rotating said cam, the block is axially-reciprocated, One

, end of the screw spindle ll'carries a sleeve 26 which, by means of the bored screw 2'1, may betightened against the body of the block 24 and 'held in position onthe block by a check nut 28.

The collar of the sleeve '26 may be clamped either securely between'the wall of the-block and screw or by allowing some slight clearance. Thus, the

screw spindle has some axial clearance with respect to the block so that, by this means, .it will be possible to finely regulate the reciprocation of the headstocks. and to bring about a slight dwell or stop at each end of a stroke.

body of the base and carry the change or pick-off gears 31 and 32 at their respective opposite ends. "The gear 31 meshes with the gear 33, and the gear 32 with gear 34.. The gears 33 and .34 are mounted on the common shaft 35 which connects to the driving shaft 3'7 over the clutch 36. The driving shaft 37 is supported within the base so as universal joint shaft 42, by means of the crank handle 43. The crank handle may be fixed in two positions by the spring-actuated bolt 44. In one of these positions, shaft 37 is shifted downwards, and the clutch 36 is disengaged so that the mechanism driving the displacing movements is thrown out of action. In the other position, the shaft 3'1 is shifted upwards, and'the clutch as well as the displacing mechanism are put into action. The driving shaft 37 is driven through the worm gearing from the motor 46. On the upper end of the shaft 35, a spiral gear 47 is mounted and meshes with another spiral gear 48, the latter driving the splined shaft 49 .which may be axially shifted within the spiral gear. I e

As far as the description beforementionedis concerned, the, driving mechanism intended for, imitating the practical displacing movements is the same and common to both the spur gear and the bevel gear lapping machines. Considering the 1.

- spur gear lapping machine, the-splined' shaft 49 said lever which may beadjusted by the set screw 1' 53, acts upon lifting the. bearing block 54 or dropping the same, the spring 55 being provided for maintaining a constant contact between the bearing .block and the set screw 53.

The bearing block 54v receives the rear bearing 54:: of the spindle 56 which is supported at the front end by thebearing 57. The bearing block 54 slides verticallywithin the guide 58. when the cam 50 rotates and thelever 51 moves up and down, the spindle swings about the centre of the pendulum bearing 57 in a .vertical plane through the axis of the spur'gear.

On the axis of the driven gear, two different brakes are arranged one of them acting as a perma'nent brake under light pressure, while the 115 7 other one serves as a hand brake permitting the use of avery high braking force. The object of the permanent brake is to. provide for a per- .manent, positive bearing of the tooth flanks 'of the gears to be lapped and for a uniform, per- 12'.)

manently acting pressure between the adjacent The endof the spindle 56 carries a collared bushing 59 secured against rotation by the key I 60. The collar. of the bushing contacts with the wall of' the bearing .block 54. A split nut 61 is-screwed, on to the bushing; after this nut has been adjusted, it may be locked against self-loosening by the screw 62. Within the nut, a ring 63 having a conical surface is forced against the conical surface of the bearingblo'ck 54 by the coiled springs, 64. The braking :force is brought about by the frictional contact between these two conical surfaces.

' The hand brake which may be actuated by the hand lever 65 pivoted at 65 (see'Fig. 2) consists 13 of a drum 66 which is keyed to the spindle and held in position by means of the adjusting ring 67. The braking band 68' which may be tight-- ened or relieved by turning the shaft by the aid of lever-65 is placed round the drum.

The variable distance between the centres of thespindles may be observedon the rule 69 with vernier 70. In addition, a dial micrometer 'll'is' provided for ea'ch'of the two headstocks so as' to be adjustable on the machine base, and a flnger touches the pointof each micrometer in order to show the readingscorresponding to the amplitudes of the individual displacing movements'.

The headstock ireceiving' the driving as 5 carries the. spindle '13 supported radially and The spindle is driven from the belt pulley 76.

Justable bolt mounted in the wall 0! the headstock prevent the spindle from rotation when the gears are to be clamped or removed.

The pump feeding the lapping compound is also common to the feasible kinds of machine designs mentioned above. It comprises a'container 78 to which is screwed the motor 79 the'shaft extension of the latter carrying a paddle wheel 80 provided withspiral blades or paddles the'direction of which'is opposite to the direction oi rotation of the paddle'wheel as well as to the spiral direction of the guide-blades 01' provided in the pump body. The paddle wheel has no metallic contact with the pump body so that any wear of the pump caused by the supply of the lapping compound is done away with. 4 The pump acting by centrifugal force presses the lapping compound through the spiral guide-blades 81 of the body '18 into the hose 82 which feeds it be- -tween.the teeth of the gears. The used compound is returned to the container through the hose 83.

The single-purpose machine as used for lapping bevel "gears, Figs. 4, 5, 11, 12, only difiers irornthe designjust described by the position of the two headstocks which are at right anglesto each other.

The headstock 84 for the driven gear 85 carries a spindle in an eccentric sleeve'8'i which may be rotatedby means of hand wheel 89 through worm and worm gear88 whereby the centre axis 86 of the g'ear may be placedabove or below the centre 90 of the sleeve 8'7, and therefore also above or below the centre of the driving bevel gear so that gears having crossing ax es may also be lappedin contradistinction to gears-with inter- The permanent brake is arranged in this headstock just: in the same manner as in the head- 1 stock of the spur gearlapping machine. Likewise, a hand brake is, provided and may be actuated by the lever 91.

The headstock 92 for ,thedrivinggear 93..carries the spindle 94 in two antifriction bearings.

namely in the front pendulum bearing 95 and in. the second bearing 96. The second bearing 96 provided with a rests in, a rotatable sleeve 97 v worm gearcut into its periphery, the bearing being arranged in a guide block 98 which may P be vertically adjusted within a square recess of 'be inclined. rotatin turning the worm. 100, the

forms a similar the sleeve-9'! by means of the set screw 99 so that the centre axis of'thebea'ring 96 may be made parallel with the centre axis of the'sleeve'9'1. By'

axis of the spindle may the sleeve. 97 by spindle axis is caused to perform a three dimensional waving or wabble this procedure, the centre motion about the centre point ofthe pendulum bearing 95 which represe As a consequence, the bevel gear 93, too, perthree-dimensionalwabble' mo- 'ts' the stationary p016.

tion which, together-with the straaiight-v line reciprocatlons' of the two" headstocksv imitates the displacing movementsoccuring :under service conditions. The .worm' 1001s; mounted on the shaft; 49 and is rotated bythe same,.when'the 'mechanis'm described above and shown iii-Figs.

- .11' and 12, is put intoaction to imitatethe actual displacing movements. 1-- j e At one end, the spindle= 4 carries abelt pulley 101 which isdriven-froma-motor 102 axially by the anti-friction bearings 74 and '15. v

Two grooves '77 which may be engaged by an ad-.

the bottom of the machine base. Said motor is mounted on a plate 103 which swings about an axis 104 to enable the motor to follow the changing positions of the belt pulley 101. To absorb vibrations the plate 103 is damped in its movements through the section of a plunger moving within a cylinderand displacing oil through narplacements they receivein service, by subjectingthe gears to three dimensional relative movements.

2. The method of lapping gears to make them run silently which consists in placing pairs of' conjugate gears in the meshed relation which they occupy in service, rotating the gears while supplying fluid grinding compound between the gear teeth, and subjecting the-gears to three dimensional relative movements of different amounts and at difierent speeds.

3. The method of producing silently running gears which consists in forming the teeth of gears with surplus material at the top and root portions thereof, placing pairs of conjugate gears in correct meshing relation, and thenlappin them with fluid abrasive while subjecting them to three'dimensional relative movements simulating all of the movements which they can receive in service. 4. A spur lapping machine comprising two headstocks capable of relative movement; two parallel rotatable gear supporting spindles, one in each of said headstocks; means for imparting-to one of said headstocks a reciprocating motion along the axis of its spindle: means for imparting a..;reciprocating motion to the other headstock; and means forimparting awabble motion to the spindle of the other headstock independently of its reciprocating motion.

5. A machine for lapping bevel gears comprising a base carrying two hea'dstocks capable of relative rotational movement; a gear supporting spindle in'each of said headstocks, said spindles being angularly disposed one to theother; means for imparting straight spindleaxis; means for impartmotion, to the other headstock its spindle axis; means for subline reciprocatiory move{ 'ment to one ,of said headstocks in a direction perone of said headstocks to.

' 6. A machine for lapping bevel gears comprising a base carrying two headstocks capable of relative rotational movement;

.means for,suhjecting the spindle of one. of said headstocks to a 'wabblej motions and eccentric v sear s pp tin -spindle in each or. said .hesdstocka-saidspindles. :being angularly disposed one to the otherinieans for imparting straight line reciprocatory' movement to one of said headstocks in a direction permeans for varying the periodicity of said wabble motion.

7'. A machine for lapping bevel gears comprising a base carrying two headstocks capable of relative rotational movement; a gear supporting spindle in each 01' said headstocks, said spindles being angularly disposed one to the other; means for imparting straight line reciprocatory movement to one of said headstocks in, a direction perpendicular toits spindle axis; means for imparting reciprocatory motion tothe other headstock perpendicular to its-spindle axis; motor-operated means for subjecting the spindle of one of said headstocks to a wabble motion; eccentric means for varying the periodicity of said wabble motion; and-means for damping the movements of said motor-operated means.

8. A machine for lapping gears comprising a frame carrying twoheadstocks; a gear-supporting spindle rotatable in each of said 'headstocks;

' means for moving each of saidheadstocks. in a direction at right angles to its spindle axis; means for raising and lowering one of said spindles; and

means for swinging one of said spindles bodily about an axis perpendicular to its own axis.

9. A machine for lapping gears comprising a frame; a plurality of headstocks mounted on said frame; a gear-supportingspindle in'each of said headstocks'; means for reciprocating each of said headstocks toward andaway from the other headstock; and micrometermeans on said frame-for measuring the amountof the reciprocations.

10. A gear lappingmachine comprising ftwo headstocks capable Iofrelative movement; two

parallel work-supporting spindles, one in eachof 7 said headstocks; means for imparting to one of said headstocks a reciprocating motion along the axis of its spindle; means for imparting a reciprocating' motion to the other headstock; means for imparting a wabble motion to the spindle of said other headstock; and means for supplying work surfaces.

11. A' machinefor lapping bevel gears, comfluid abrasive compound under pressure to the prising a base carrying two headstocks capable.

Patent No. 1,966,172.

HERMANN JAC-KOWSlil.

4 CERTIFICATE OF memories;

stock perpendicular to its spindle axis; motor operated eccentric meains for subjecting the spindle in said other headstock to a wabble motion; and means for varying the period and extent-of each of the motions independently of the other motions.

12. A machine for lapping gears, comprising a frame; a plurality of headstocks mounted on the frame; a gear supporting spindle in each of said headstocks; means ior reciprocating each of said headstocks; means for imparting a wabble motion to one of said spindles; a motor for imparting the wabble motion to said gear supporting' .spindle; "and means for dampingthe'vibrations of said driving motor.

13. A machine for lapping gears, comprising a frame-carrying two headstock's.;. a gear support!- ing spindle rotatable in each of said headstock's;

1 means for imparting straight line reciprocatory movements to each of said headstocks;-' meansfor imparting a wabble motion to one oi the two spindles; and means for adjusting one ,of said spindles to positions above 'orbelow thejcenter of the other spindle! 14. A machine for lapping gears, comprising a 10 frame carrying two headstocks," a ear su'pporting spindle rofatablein each of said 'headstocks; means for reciprocating eachvoi' said headstocks; and means for swinging oneof said spindles bodily about an axis perpendicular to itself.

15. A gear lapping machine, comprising two Vheadstocks capable of relative rotational movement; two work supporting'spindles, one in each of said headstocks; means for imparting to both of said headstocks a reciprocating motion; means 11 for imparting a wabble' motion to 'the spindle of one of thetw ohea dstocks; and means for supplying fluid abrasive compound under pressur to the work carried by said spindles. 4 a

16. The method of'producing silently running i intermeshed gears, which consists in forming the hardened gear teeth with excess material at the top and root portions and projecting'beyond the confines of the' correct involute profile, placing pairs of conjugate gears in correct meshing relay- 2 tion, and then-lapping thegears with fluid abras sive while rotating them and subjecting the two gears to 'movementsirelative to each other three .planes until the excess material is ground away and; the profileof the finished gearis shaped to-correct involute form.

' HERMANN JACKQWSK L- it "is hereby certified that error appears in the printed specification-of the.

above numbered patent requiring correction-as ioll iws: Page. 4, line 'ME' fllfiihl I of the case in the Patent Office.

A insert the. word gear; and that thesaid Letters Patenthe read'wiih this correction therein'that the same may conform tq-Ithe m ie-Fra ier v I I means for varying the periodicity of said wabble motion.

7'. A machine for lapping bevel gears comprising a base carrying two headstocks capable of relative rotational movement; a gear supporting spindle in each 01' said headstocks, said spindles being angularly disposed one to the other; means for imparting straight line reciprocatory movement to one of said headstocks in, a direction perpendicular toits spindle axis; means for imparting reciprocatory motion tothe other headstock perpendicular to its-spindle axis; motor-operated means for subjecting the spindle of one of said headstocks to a wabble motion; eccentric means for varying the periodicity of said wabble motion; and-means for damping the movements of said motor-operated means.

8. A machine for lapping gears comprising a frame carrying twoheadstocks; a gear-supporting spindle rotatable in each of said 'headstocks;

' means for moving each of saidheadstocks. in a direction at right angles to its spindle axis; means for raising and lowering one of said spindles; and

means for swinging one of said spindles bodily about an axis perpendicular to its own axis.

9. A machine for lapping gears comprising a frame; a plurality of headstocks mounted on said frame; a gear-supportingspindle in'each of said headstocks'; means for reciprocating each of said headstocks toward andaway from the other headstock; and micrometermeans on said frame-for measuring the amountof the reciprocations.

10. A gear lappingmachine comprising ftwo headstocks capable Iofrelative movement; two

parallel work-supporting spindles, one in eachof 7 said headstocks; means for imparting to one of said headstocks a reciprocating motion along the axis of its spindle; means for imparting a reciprocating' motion to the other headstock; means for imparting a wabble motion to the spindle of said other headstock; and means for supplying work surfaces.

11. A' machinefor lapping bevel gears, comfluid abrasive compound under pressure to the prising a base carrying two headstocks capable.

Patent No. 1,966,172.

HERMANN JAC-KOWSlil.

4 CERTIFICATE OF memories;

stock perpendicular to its spindle axis; motor operated eccentric meains for subjecting the spindle in said other headstock to a wabble motion; and means for varying the period and extent-of each of the motions independently of the other motions.

12. A machine for lapping gears, comprising a frame; a plurality of headstocks mounted on the frame; a gear supporting spindle in each of said headstocks; means ior reciprocating each of said headstocks; means for imparting a wabble motion to one of said spindles; a motor for imparting the wabble motion to said gear supporting' .spindle; "and means for dampingthe'vibrations of said driving motor.

13. A machine for lapping gears, comprising a frame-carrying two headstock's.;. a gear support!- ing spindle rotatable in each of said headstock's;

1 means for imparting straight line reciprocatory movements to each of said headstocks;-' meansfor imparting a wabble motion to one oi the two spindles; and means for adjusting one ,of said spindles to positions above 'orbelow thejcenter of the other spindle! 14. A machine for lapping gears, comprising a 10 frame carrying two headstocks," a ear su'pporting spindle rofatablein each of said 'headstocks; means for reciprocating eachvoi' said headstocks; and means for swinging oneof said spindles bodily about an axis perpendicular to itself.

15. A gear lapping machine, comprising two Vheadstocks capable of relative rotational movement; two work supporting'spindles, one in each of said headstocks; means for imparting to both of said headstocks a reciprocating motion; means 11 for imparting a wabble' motion to 'the spindle of one of thetw ohea dstocks; and means for supplying fluid abrasive compound under pressur to the work carried by said spindles. 4 a

16. The method of'producing silently running i intermeshed gears, which consists in forming the hardened gear teeth with excess material at the top and root portions and projecting'beyond the confines of the' correct involute profile, placing pairs of conjugate gears in correct meshing relay- 2 tion, and then-lapping thegears with fluid abras sive while rotating them and subjecting the two gears to 'movementsirelative to each other three .planes until the excess material is ground away and; the profileof the finished gearis shaped to-correct involute form.

' HERMANN JACKQWSK L- it "is hereby certified that error appears in the printed specification-of the.

above numbered patent requiring correction-as ioll iws: Page. 4, line 'ME' fllfiihl I of the case in the Patent Office.

A insert the. word gear; and that thesaid Letters Patenthe read'wiih this correction therein'that the same may conform tq-Ithe m ie-Fra ier v I I 

